JPH0268948A - Fitting method of wafer to wafer stage - Google Patents

Abstract

PURPOSE:To prevent reduction in patterning accuracy being based on thermal deformation by sucking a wafer to the fitting surface of the water stage with a specified suction force by wafer suction means, reducing suction force of the wafer suction means temporarily, and then sucking the wafer to the fitting surface of the wafer stage by the wafer suction means. CONSTITUTION:In an aligner provided with a wafer stage 5 having a wafer suction means and a transfer means 2 for transferring a wafer 1 and passing it to the wafer stage 5, the wafer transferred to the wafer fitting surface 6 of the wafer stage 5 is sucked to the fitting surface 6 with a specified suction force by the above wafer suction means, and then suction force of the above wafer suction means is temporarily reduced, then the wafer 1 is sucked to the fitting surface 6 of the wafer stage 5 by means of the wafer suction means. For example, the above wafer suction means is a vacuum chuck. Then, when reducing the suction force of the above wafer suction means temporarily, the wafer 1 is retained by the above transfer means 2 and the suction force is cancelled by the wafer suction means.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an exposure apparatus that exposes a pattern image drawn on a mask onto a substrate such as a wafer coated with a photosensitive agent.
The present invention relates to a wafer mounting method for mounting a wafer on a wafer stage that holds the wafer during exposure, and particularly relates to an improvement for preventing deterioration in pattern accuracy due to deformation into sea urchins due to temperature changes.

[Prior Art] FIG. 6 shows the mounting direction of a wafer on a wafer stage (support stand) in a conventional exposure apparatus. FIG. 4 schematically shows the internal configuration of the exposure apparatus. The pressure between the groove 3 and the wafer is reduced by exhausting the gas between the groove 3 and the wafer 1, which communicate with the exhaust hole 4, using a rotary pump or the like through the exhaust hole 4 provided in the wafer hand 2. The wafer 1 is attracted to the wafer hand 2 by this differential pressure, which is smaller than the pressure applied to the surface. This is a method called vacuum chuck, and if the force due to the differential pressure (the product of the differential pressure and the area of the groove) is greater than the weight of the wafer, the wafer 1 can be held in the wafer hand 2 without falling. After the wafer hand 2 takes out and mounts the wafer 1 from a wafer cassette (not shown) or the like, the wafer hand 2 is moved, and the wafer 1 is placed on the wafer stage so that the center axis of the wafer mounting surface 5 and the center axis of the wafer 1 almost match. Align the position on the wafer mounting surface 6 of No. 5. Next, the exhaust from the exhaust hole 4 of the wafer hand 2 is stopped, the exhaust hole 4 is allowed to leak, and the pressure of the exhaust hole 4 is raised to the atmospheric pressure of the wafer 1. As a result, the difference between the atmospheric pressure of the wafer 1 and the pressure between the groove 3 and the wafer 1 is almost eliminated, and the attraction force between the wafer 1 and the wafer hand 2 is also almost eliminated. Next, the space between the wafer 1 and the groove 7 provided in the wafer mounting surface 6 that communicates with the exhaust hole 8 is evacuated from the exhaust hole 8 provided in the wafer stage 5 using a rotary pump or the like. Similarly, the wafer 1 is attracted onto the wafer mounting surface 6 of the wafer stage 5. At this point, the wafer hand 2 is separated from the wafer 1 to complete the wafer mounting.

After the wafer mounting is completed, in the exposure apparatus having the configuration shown in Fig. 4,
The mask 9 and the wafer 1 are accurately aligned and exposed. By the way, the line width formed on a wafer by so-called submicron exposure, that is, exposure is 0. A few μm
Furthermore, when the thickness becomes about 0.2 μm, the temperature of the wafer 1 and the wafer stage 5 must be adjusted with high precision. This means that when the exposure area of a wafer is a square with a diagonal length of 40 mm, if there is a temperature change of 23 ± 0.1 t in that area, the temperature change will be 0.02 μ for a Si (silicon) wafer.
If the wafer mounting surface 6 of m1 wafer stage 5 is made of quenched AIL, it is 0.07 μm, and if it is made of AJZ, it is 0.12 μm.
This is because the length changes by m. Generally, the adsorption force of the wafer mounting surface is sufficiently large, and most of the parts are larger than the shear stress due to heat between the wafer 1 and the wafer mounting surface 6, so the wafer 1 is restrained by the wafer mounting surface 6, and the wafer mounting surface The thermal expansion of 6 causes thermal deformation of the wafer 1. Therefore, as mentioned above, within the exposure area 0.07~
The length of the wafer 1 changes by about 0.12 μm. This is an amount that cannot be ignored in an exposure apparatus with a resolution of 0.2 μm. Therefore, as shown in FIG. 6, a flow path 11 is provided in the wafer stage 5, and a cooling medium 12 whose temperature is controlled with high precision is passed therethrough, so that the wafer stage 5, which has a large heat capacity, is heated to, for example, 23±0.02°C. Keep the wafer mounting surface 6
And the temperature of the wafer 1 is controlled with high precision. Furthermore, it is desirable to control the temperature of the exposure atmosphere 13 inside the exposure chamber 10 with high precision as well, but since the volume of the exposure atmosphere 13 is large and there are many heat sources such as actuators and motors inside the exposure chamber 10, It is difficult to control the temperature with high precision, and in reality, the temperature is controlled with medium precision, for example, 23±0.1°C.

[Problems to be Solved by the Invention] However, in the prior art, the exposure atmosphere 1
The temperature of No. 3 is controlled with only medium accuracy, and the wafer 1, which is approximately equal to this temperature, may be deformed to such an extent that the influence on resolution cannot be ignored due to thermal fluctuations. When this deformed wafer 1 is adsorbed to a wafer mounting surface with sufficient adsorption force, the adsorption force is
Since most of the parts are larger than the shear stress due to heat between the wafer mounting surface 6 and the wafer mounting surface 6, the wafer mounting surface 6 is suctioned and fixed in its deformed shape. Since exposure is performed in such a state, there are problems such as (1) the pattern of the mask 9 cannot be transferred to the wafer 1 with high precision, and (2) the mask 9 and the wafer 1 cannot be aligned with high precision. there were.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a method for mounting a wafer on a wafer stage, which prevents deterioration in patterning accuracy due to thermal deformation.

[Means and Operations for Solving the Problems] According to the invention, in an exposure apparatus equipped with a wafer stage having a wafer suction means and a transfer means for transferring and delivering the wafer to the wafer stage, The wafer transferred to the wafer mounting surface of the wafer stage by the transfer means is adsorbed onto the mounting surface by the wafer adsorption means with a predetermined adsorption force, then the adsorption force of the wafer adsorption means is weakened once, and then the wafer is adsorbed again. The wafer can be mounted by suctioning the wafer onto the mounting surface of the wafer stage, or in an exposure apparatus equipped with a wafer stage having a wafer suction means and a temperature adjustment means for maintaining the wafer stage within a temperature range with a predetermined accuracy. By bringing the wafer to be processed into contact with an object whose temperature has been adjusted to a predetermined accuracy to bring the temperature to the same degree of accuracy as the wafer stage, and then adsorbing the wafer to the mounting surface of the wafer stage by the wafer adsorption means, The wafer is mounted on a wafer stage in a state in which the amount of deformation of the wafer due to temperature fluctuation is smaller than the amount of deformation allowed when transferring a mask pattern with high precision.

[Example] FIG. 1 sequentially shows a first embodiment of the present invention.

In the figure, 1 is a wafer, 2 is a wafer hand for holding and moving the wafer 1, 3 is a groove provided in the wafer hand 2 to vacuum chuck the wafer 1 to the wafer hand 2, and 4 is connected to the groove 3. The exhaust hole 5 is connected to the wafer 1 during exposure.
6 is a wafer mounting surface; 7 is a groove provided in the wafer mounting surface 6 for adsorbing the wafer 1; 8 is a wafer stage supporting the wafer 1;
11 is a flow path for circulating cooling water provided in the wafer stage 5; 12 is the cooling water; and 13 is the atmosphere surrounding the wafer 1, wafer hand 2, and wafer stage 5.

In the above configuration, a method for mounting the wafer 1 on the wafer mounting surface 6 of the wafer stage 5 will be described below. The wafer 1 is attracted to the wafer hand 2 using a vacuum chuck from a cassette (not shown) or the like. The wafer hand 2 is moved and aligned so that the center of the wafer mounting surface 6 and the center of the wafer 1 substantially coincide with each other. At this time, wafer 1
The temperature of the atmosphere 13 is almost the same as that of the atmosphere 13. However, this atmospheric temperature is a medium-accurate temperature control, for example, 23 ± 0.
．． 1 t: Therefore, the length between the two diagonal points ab of the square exposure area is
If the temperature is 23℃ and it is 40mm, then 40mm±0.
02 μm. Thereafter, the wafer 1 is suctioned onto the wafer mounting surface 6 by a vacuum chuck, and the suction force of the wafer hand 2 is eliminated. At this time, the wafer 1 is in a deformed state as described above, and the adsorption force of the wafer mounting surface 6 is sufficiently large to prevent the wafer 1 from falling or shifting its position. As shown in FIG.
℃), the wafer 1 is adsorbed onto the wafer mounting surface in a deformed state with an a-b length of 40+nm±0.02 μm. In this case, since the wafer 1 is attracted to the wafer mounting surface 6 with a sufficiently large force, the contact area between the wafer 1 and the wafer mounting surface 6 is large, and the heat capacity of the wafer stage 5 is large, so the temperature of the wafer 1 decreases in a few seconds. The temperature is the same as that of wafer stage 5, 23±0.02°C.

Next, we move on to the most characteristic operation of the present invention. That is, the wafer 1 is vacuum evacuated through the exhaust hole 4 of the wafer hand 2.
is sucked and held again by wafer hand 2 (vacuum chuck)
do. When this suction and holding by the wafer hand 2 is completed, the exhaust hole 8 of the wafer stage 5 is leaked and opened to the atmosphere, and the suction force between the wafer mounting surface 6 and the wafer 1 is released. As a result, the wafer 1 is released from the shape-restricting force due to the adsorption force of the wafer mounting surface 6, and the length between two points ab on the wafer 1 becomes 40 mm±0.00-several μm almost instantaneously. Immediately thereafter, the space between the suction groove 7 on the wafer mounting surface 6 and the wafer 1 is evacuated and depressurized through the exhaust hole 8 of the wafer stage 5 to generate suction force, and the wafer 1 is again suction-held on the wafer stage 5 (vacuum chuck )do. When the suction and holding by the wafer stage 5 is completed, the exhaust hole 4 provided in the wafer hand 2 is leaked and opened to the atmosphere, and the suction force between the wafer hand 2 and the wafer 1 is released. away from. At this time, the wafer mounting surface 6
The distance between two points ab on wafer 1 that are attracted to is 40 mm.
The amount of deformation within the exposure area of the wafer 1 is several 0.00 μm, so the wafer 1 and the mask 9
It has almost no effect on high precision alignment and high resolution of 0.02 μm.

In the above embodiment, the wafer hand 2 and the wafer stage 5 used a vacuum chuck to attract the wafer 1, but an electrostatic chuck, a magnetic chuck, or the like may be used in place of the vacuum chuck.

A second embodiment of the invention is shown in sequence in FIG.

The same members as in the embodiment of FIG. 1 are given the same numbers. Further, the temperature control conditions for the atmosphere 13 and the cooling medium 12 are the same as in the first embodiment described above.

The wafer 1 is attracted to the wafer hand 2 by a vacuum chuck from a cassette (not shown) or the like. The wafer hand 2 is moved to bring the wafer 1 and the wafer mounting surface 6 into contact so that the center of the wafer 1 and the center of the wafer mounting surface 6 are aligned and the wafer 1 and the wafer mounting surface 6 are parallel to each other. This state is maintained until the temperature of the wafer 1 reaches approximately the temperature of the wafer mounting surface 6, for example, 23±0.02°C.

To determine the time to maintain this state, perform the same operation using wafer 1 equipped with a temperature sensor, calculate in advance the time until the temperature starts to be controlled to 23 ± 0.02°C, and then attach wafer 1 and wafer for that period of time. It is sufficient if the surface 6 is kept in contact with the surface 6. As a result of this operation, the length between two points ab on the wafer 1 becomes approximately 40 mm: th: several 0.00 μm. next,
After the wafer 1 is attracted to the wafer mounting surface 6 by a vacuum chuck, the attraction force of the wafer hand 2 is removed and the wafer hand 2 is separated from the wafer 1. The method described above also provides the same effects as the first embodiment described above. However, compared to the first embodiment, the wafer 1 and the wafer mounting surface 6 are attracted to each other in order to bring the temperature of the wafer 1 to 23±0°02°C before vacuum chucking the wafer 1 to the wafer mounting surface 6. Since there is no contact area, the contact area is small and the temperature of wafer 1 is 23±0.
．． It takes longer to reach 02°C.

A wafer stage for carrying out the third embodiment of the present invention is shown in FIG. In the figure, reference numerals 14 and 15 indicate grooves for a vacuum chuck provided in the wafer mounting surface 6, reference numeral 16 indicates an exhaust hole communicating with the groove 14, and reference numeral 17 indicates an exhaust hole communicating with the groove 15.

By moving the wafer 1 vacuum chucked by the wafer hand 2 so that its center and the center of the wafer mounting surface 6 almost coincide with each other, bringing the wafer 1 into contact with the wafer mounting surface 6, and evacuating through the exhaust hole 17. , the wafer 1 is suctioned and held on the wafer mounting surface 6 via the central groove 15. Thereafter, the suction force of the wafer hand 2 is removed, and the wafer hand 2 is separated from the wafer 1. At this time, as shown in FIG. 3, even if the wafer 1 is vacuum chucked, the groove 15 does not have a structure that restrains the deformation of the wafer 1 due to heat-induced shear stress between it and the wafer mounting surface 6, so the heat capacity is reduced. If the sufficiently large wafer stage 5 is temperature-controlled to a temperature of 23±0.02°C with high precision, by maintaining this state, the temperature of the wafer 1 can be controlled to 23±0.02°C, and the temperature of the wafer 1 can be controlled to 23±0.02°C. The length between the two points ab on the top is approximately 40 mm ± 0.00 several μ
It can be m. The time required for this contact is
It can be determined by the same method as in the example. After that, the exhaust hole 16 of the wafer stage 5 is also evacuated, and a sufficiently large wafer 1 is vacuum-adsorbed on the entire wafer mounting surface, and the planar deformation such as warpage of the wafer 1 is removed by a wafer mounting surface with sufficient flatness. Correct it with , and move on to the exposure operation. The above embodiment also provides the same effects as the first embodiment. However, in this case as well, the wafer temperature is 2.
It takes a long time to reach 3±0.02°C. However, the parallelism between the plane of the wafer hand 2 and the wafer mounting surface 6 is not necessary in the second embodiment.

Due to the structure of the wafer stage shown in FIG. 3, in the first embodiment, after the evaporator 1 is once attracted to the wafer mounting surface 6, it is supported by the wafer hand 2 to eliminate the attraction force of the wafer mounting surface 6. However, the same effect can be obtained by eliminating the suction force of the groove 14 while leaving only the suction force of the groove 15 without using the wafer hand 2.

[Effects of the Invention] As explained above, just before the wafer is finally suctioned and fixed to the wafer mounting surface, the wafer's heat can be reduced by bringing the wafer into contact with an object whose temperature is precisely controlled, for example, the wafer mounting surface. It is possible to prevent a decrease in resolution due to distortion and an increase in alignment errors between the mask and the wafer.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the first embodiment of the present invention in order 1, FIG. 2 is an explanatory diagram showing the second embodiment of the present invention in order, and FIG. 3 is the third embodiment of the present invention. FIG. 4 is an internal configuration diagram of an exposure apparatus to which the present invention is applied, FIG. 5 is an explanatory diagram of a wafer exposure area, and FIG. 6 is a diagram showing a conventional wafer mounting method. It is an explanatory diagram of operation shown in order. 1: Wafer, 2: Wafer hand, 3.7, 14, 15: Groove, 4.8, 16, 17: Exhaust hole, 5: Wafer stage, 6: Wafer mounting surface, 9: Mask, 11: Channel. Patent Applicant Canon Co., Ltd. Agent Patent Attorney Tetsuya Ito Agent Patent Attorney Tatsuo Ito Figure 4

Claims (7)

[Claims] (1) In an exposure apparatus equipped with a wafer stage having a wafer suction means and a transfer means for transferring the wafer and delivering it to the wafer stage, the wafer is transferred to the wafer mounting surface of the wafer stage by the transfer means. The wafer is adsorbed onto the mounting surface with a predetermined adsorption force by the wafer adsorption means, and then the adsorption force of the wafer adsorption means is temporarily weakened;
A method for mounting a wafer on a wafer stage, characterized in that the wafer is then sucked onto the mounting surface of the wafer stage again by a wafer suction means. (2) When the suction force of the wafer suction means is once weakened, the wafer is held by the transfer means and the suction force of the wafer suction means is released. How to attach to wafer stage. (3) The wafer suction means is composed of a plurality of suction parts provided on the wafer mounting surface of the wafer stage, and when the suction force of the wafer suction means is once weakened, the wafer suction means except for some of the plurality of suction parts 2. The method of mounting a wafer on a wafer stage according to claim 1, wherein the wafer is held on the mounting surface by some of the suction parts while releasing the suction force of the other suction parts. (4) In an exposure apparatus equipped with a wafer stage having a wafer suction means and a temperature adjustment means for maintaining the wafer stage within a temperature range with a predetermined accuracy, the wafer to be mounted is placed at a temperature with the same degree of accuracy as the wafer stage. A method for mounting a wafer on a wafer stage, characterized in that the wafer is then sucked onto a mounting surface of the wafer stage by the wafer suction means. (5) The wafer is brought into contact with a wafer stage without being suctioned by the wafer suction means, so that the temperature is brought to the same level of accuracy as that of the wafer stage. How to attach the wafer to the wafer stage. (6) The exposure apparatus is characterized in that it is equipped with a transfer means for transferring the wafer to be mounted and delivering it to the wafer stage, and the transfer means brings the wafer into contact with the wafer stage while holding the wafer. A method for mounting a wafer on a wafer stage according to claim 5. (7) The wafer suction means is composed of a plurality of suction parts provided on the wafer mounting surface of the wafer stage, and removes the suction force of the other suction parts except for some of the plurality of suction parts. 6. The method of mounting a wafer on a wafer stage according to claim 5, wherein the wafer is brought into contact with the wafer stage by holding the wafer on the mounting surface by a suction section of the wafer.